The disposal of nuclear waste discharged with the spent fuel from a fission nuclear power plant is one of the most important environmental safety issues faced by the nuclear power industry. This issue is hindering the use of nuclear power in a safe, abundant, efficient, and proliferation-resistant manner. Isotopes responsible for the majority of the external gamma exposure in fuel reprocessing plants are 137Cs and 90Sr in the form of dissolved ions. High level waste (HLW) contains primarily the fission radionuclides 137Cs and 90Sr and very small amounts of transuranic radionuclides. (See, “Development of matrices for vitrification of strontium and cesium concentrate from high-level waste”; Aloi, A. S.; Trofimenko, A. V.; Iskhakova, O. A.; Kolycheva, T. I.; Radiochemistry 1997, 39, 567-573; “Cesium removal demonstration using selected actual waste samples from the Hanford reservation tank farm”; Peterson, R. A.; Fiskum, S. K.; Arm, S. T.; Blanchard, D. L.; Separation Science and Technology 2006, 41, 2361-2371; and “Demonstration of the caustic-side solvent extraction process for the removal of (CS)—C-137 from Savannah River Site high level waste”; Norato, M. A.; Beasley, M. H.; Campbell, S. G.; Coleman, A. D.; Geeting, M. W.; Guthrie, J. W.; Kennell, C. W.; Pierce, R. A.; Ryberg, R. C.; Walker, D. D.; Law, J. D.; Todd, T. A.; Separation Science and Technology 2003, 38, 2647-2666.) Various processes exist to convert HLW into a variety of forms including alkaline or acidic supernatant liquid, sludge, salt cake, or calcine solid, however, further improvements and breakthroughs are necessary to resolve this issue.
Cesium is often removed from waste waters in the nuclear industry by means of solid ion-exchangers, ranging from organic polymers (see, “The universal solvent extraction (UNEX) process. II. Flowsheet development and demonstration of the UNEX process for the separation of cesium, strontium, and actinides from actual acidic radioactive waste”; Law, J. D.; Herbst, R. S.; Todd, T. A.; Romanovskiy, V. N.; Babain, V. A.; Esimantovskiy, V. M.; Smirnov, I. V.; Zaitsev, B. N.; Solvent Extraction and Ion Exchange 2001, 19, 23-36; and “Selective transport of cesium and strontium ions through polymer inclusion membranes containing calixarenes as carriers”; Arena, G.; Contino, A.; Magri, A.; Sciotto, D.; Lamb, J. D.; Supramolecular Chemistry 1998, 10, 5-15), compounds (see, “Decontamination of high-level waste using a continuous precipitation process”; Peterson, R. A.; Burgess, J. O.; Walker, D. D.; Hobbs, D. T.; Serkiz, S. M.; Barnes, M. J.; Jurgensen, A. R.; Separation Science and Technology 2001, 36, 1307-1321) and macrocycles (see, “A robust alkaline-side CSEX solvent suitable for removing cesium from Savannah River high level waste”; Bonnesen, P. V.; Delmau, L. H.; Moyer, B. A.; Leonard, R. A.; Solvent Extraction and Ion Exchange 2000, 18, 1079-1107; and “Actinide, strontium, and cesium removal from Hanford radioactive tank sludge”; Lumetta, G. J.; Wagner, M. J.; Carlson, C. D.; Solvent Extraction and Ion Exchange 1996, 14, 35-60) to inorganic solids such as zeolites (see, “The effect of amorphization on the Cs ion exchange and retention capacity of zeolite-NaY”; Gu, B. X.; Wang, L. M.; Ewing, R. C.; Journal of Nuclear Materials 2000, 278, 64-72; “Ion exchange selectivity of phillipsite for Cs and Sr as a function of framework composition”; Adabbo, M.; Caputo, D.; de Gennaro, B.; Pansini, M.; Colella, C.; Microporous and Mesoporous Materials 1999, 28, 315-324; “The removal of strontium and cesium from simulated hanford groundwater using inorganic ion exchange materials”; Sylvester, P.; Clearfield, A.; Solvent Extraction and Ion Exchange 1998, 16, 1527-1539; “Adsorption Behavior of Cesium and Strontium on Synthetic Zeolite-P”; Mimura, H.; Akiba, K.; Journal of Nuclear Science and Technology 1993, 30, 436-443; “Removal of Heat-Generating Nuclides from High-Level Liquid Wastes through Mixed Zeolite Columns”; Mimura, H.; Akiba, K.; Igarashi, H.; Journal of Nuclear Science and Technology 1993, 30, 239-247; and “Distribution and Fixation of Cesium and Strontium in Zeolite-a and Chabazite”; Mimura, H.; Kanno, T.; Journal of Nuclear Science and Technology 1985, 22, 284-291).
Inorganic ion exchangers possess a number of advantages as Sr2+ and Cs+ adsorbents over conventional organic ion-exchange resins, including superior chemical, thermal and radiation stability. (See, “Ion exchange properties of a cesium ion selective titanosilicate”; Bortun, A. I.; Bortun, L. N.; Clearfield, A.; Solvent Extraction and Ion Exchange 1996, 14, 341-354; and “Highly selective inorganic crystalline ion exchange material for Sr2+ in acidic solutions”; Nenoff, T. M.; Miller, J. E.; Thoma, S. G.; Trudell, D. E.; Environmental Science & Technology 1996, 30, 3630-3633). Because the primary chemical components of alkaline supernatants are sodium nitrate and sodium hydroxide, the majority of these could be disposed of as low level waste if radioactive 137Cs could be selectively removed. However, recovery of long lived radionuclides from waste solutions containing large concentrations of salt has been a challenging task. Up to now solutions based on organic crown ethers (and macrocycles) and inorganic oxide ion-exchange materials (such as clays, zeolites, alkali metal titanium silicates, manganese oxides, etc.), liquid ionic technologies have been tested and have been moderately effective. (See, “The effect of amorphization on the Cs ion exchange and retention capacity of zeolite-NaY”; Gu, B. X.; Wang, L. M.; Ewing, R. C.; Journal of Nuclear Materials 2000, 278, 64-72; “Selective exchange and fixation of strontium ions with ultrafine Na-4-mica”; Kodama, T.; Harada, Y.; Ueda, M.; Shimizu, K.; Shuto, K.; Komarneni, S.; Langmuir 2001, 17, 4881-4886; “Sorption of Am(III), U(VI) and Cs(I) on sodium potassium fluorophlogopite, an analogue of the fluorine mica mineral”; Saxena, A.; Tomar, R.; Murali, M. S.; Mathur, J. N.; Journal of Radioanalytical and Nuclear Chemistry 2003, 258, 65-72; “Separation of cesium and strontium by potassium nickel hexacyanoferrate(II)-loaded zeolite A”; Mimura, H.; Kimura, M.; Akiba, K.; Onodera, Y.; Journal of Nuclear Science and Technology 1999, 36, 307-310; “Integrated experimental and computational methods for structure determination and characterization of a new, highly stable cesium silicotitanate phase, Cs2TiSi6O15 (SNL-A)”; Nyman, M.; Bonhomme, F.; Teter, D. M.; Maxwell, R. S.; Gu, B. X.; Wang, L. M.; Ewing, R. C.; Nenoff, T. M.; Chemistry of Materials 2000, 12, 3449-3458; “Chromatographic-Separation of Strontium and Cesium with Mixed Zeolite Column”; Mimura, H.; Kobayashi, T.; Akiba, K.; Journal of Nuclear Science and Technology 1995, 32, 60-67; “Separation of Heat-Generating Nuclides from High-Level Liquid Wastes through Zeolite Columns”; Mimura, H.; Akiba, K.; Journal of Nuclear Science and Technology 1994, 31, 463-469; “Titanium silicates, M3HTi4O4(SiO4)34H2O (M=Na+, K+), with three-dimensional tunnel structures for the selective removal of strontium and cesium from wastewater solutions”; Behrens, E. A.; Clearfield, A.; Microporous Materials 1997, 11, 65-75; “Syntheses, crystal structures, and ion-exchange properties of porous titanosilicates, M3HTi4O4(SiO4)34H2O (M=H+, K+, Cs+), structural analogues of the mineral pharmacosiderite”; Behrens, E. A.; Poojary, D. M.; Clearfield, A.; Chemistry of Materials 1996, 8, 1236-1244; “Sorption behavior of radionuclides on crystalline synthetic tunnel manganese oxides”; Dyer, A.; Pillinger, M.; Newton, J.; Harjula, R.; Moller, T.; Amin, S.; Chemistry of Materials 2000, 12, 3798-3804; and “Layered metal sulfides: Exceptionally selective agents for radioactive strontium removal”; Manos, M. J.; Ding, N.; Kanatzidis, M. G.; Proceedings of the National Academy of Sciences of the United States of America 2008, 105, 3696-3699.) There are, however, drawbacks to these approaches including cost, stability and selectivity.
The compounds A2xMxSn3-xS6 (x=0.1-0.95; A=Li+, Na+, K+, Rb+; M=Mn2+, Mg2+, Zn2+, Fe2+) (e.g., “KMS”) have been reported as agents for radioactive strontium removal. (See, “Layered metal sulfides: Exceptionally selective agents for radioactive strontium removal”; Manos, M. J.; Ding, N.; Kanatzidis, M. G.; Proceedings of the National Academy of Sciences of the United States of America 2008, 105, 3696-3699.) However, it would be helpful to have additional compounds for remediation applications.
Like nuclear waste, heavy metal contamination in water poses a significant environmental hazard. Mercuric (Hg2+) and other soft heavy metal ions such as Cd2+ and Pb2+ represent major contaminants in natural water sources and industrial waste water and constitute a threat for humans and other species. (See, T. W. Clarkson in Heavy metals in the environment (Ed.: B. Sarkar) Marcel Dekker Inc., 2002, pp. 457-502.) Conventional ion-exchangers such as zeolites and clays and adsorbents, such as activated carbon generally have low selectivity and weak binding affinity for soft metal ions. (See, G. Blanchard, M. Maunaye, G. Martin, Water Res. 1984, 18, 1501-1507; A. Benhammou, A. Yaacoubi, L. Nibou, B. Tanouti, J. Colloid. Interface Sci. 2005, 282, 320-326; and C. P. Huang, D. W. Blankenship, Water Res. 1984, 18, 37-46.) Thiol-functionalized adsorbents, including clays, resins, organoceramics and mesoporous silicates, are considered the most effective sorbents for soft heavy metal ions and in particular for Hg2+. (See, R. Celis, M. C. Hermosin, J. Cornejo, Environ. Sci. Technol. 2000, 34, 4593-4599; I. L. Lagadic, M. M. Mitchell, B. D. Payne, Environ. Sci. Technol. 2001, 35, 984-990; S. Chiarle, M. Ratto, M. Rovvati, Water Res. 2000, 34, 2971-2978; D. Kara, Anal. Let. 2005, 38, 2217-2230; A. M. Nam, L. L. Tavlarides, Solvent Extract. Ion. Exch. 2003, 21, 899-913; J. S. Lee, S. Gomez-Salazar, L. L. Tavlarides, React. Funct. Polym. 2001, 49, 159-172; A. M. Nam, S. Gomez-Salazar, L. L. Tavlarides, Ind. Eng. Chem. Res. 2003, 42, 1955-1964; X. Feng, G. E. Fryxell, L.-Q. Wang, A. Y. Kim, J. Liu, K. M. Kemner, Science 1997, 276, 923-926; J. Liu, X. Feng, G. E. Fryxell, L.-Q Wang, A. Y. Kim, M. Gong, Adv. Mater. 1998, 10, 161-165; X. Chen, X. Feng, J. Liu; G. E. Fryxell, M. Gong, Sep. Sci. Technol. 1999, 34, 1121-1132; L. Mercier, T. J. Pinnavaia, Adv. Mater. 1997, 9, 500-503; L. Mercier, T. J. Pinnavaia, Environ. Sci. Technol. 1998, 32, 2749-2754; J. Brown, L. Mercier, T. J. Pinnavaia, Chem. Commun. 1999, 69-70; C.-C Chen, E. J. McKimmy, T. J. Pinnavaia, K. F. Hayes, Environ. Sci. Technol. 2004, 38, 4758-4762; S. J. L. Billinge, E. J. McKimmy, M. Shatnawi, H. Kim, V. Petkov, D. Wermeille, T. J. Pinnavaia, J. Am. Chem. Soc. 2005, 127, 8492-8498; J. Brown, R. Richer, L. Mercier, Microp. Mesop. Mater. 2000, 37, 41-48; L. Mercier, C. Detellier, Environ. Sci. Technol. 1995, 29, 1318-1323.) In addition, mesoporous carbon materials with thiopyrene functional groups were proven to be excellent sorbents for mercuric ions. (See, Y. S. Shin, G. Fryxell, W. Y. Um, K. Parker, S. V. Mattigod, R. Skaggs, Adv. Funct. Mater. 2007, 17, 2897-2901.) More recently, iron oxide nanoparticles coated with humic acid showed remarkable capability to remove heavy metal ions (Hg2+, Pb2+, Cd2+, Cu2+) from water. (See, J.-F. Liu, Z.-S Zhao, G.-B. Jiang, Environ. Sci. Technol. 2008, 42, 6949-6954.) However, additional and improved waste water remediation compounds for heavy metal contamination are desired.
Crude oil and unprocessed gas can contain significant amounts of elemental mercury and chemically bound mercury. Raw produced hydrocarbon liquids also contain organic mercury compounds that partition into particular product streams in distillations and separations. Mercury is harmful to petroleum handling and processing systems because in gas processing, mercury can damage equipment, including cryogenic heat exchangers. Also, mercury poisons catalysts and becomes a component of waste water, which negatively impacts regulatory compliance. (See Wilhelm, S M; Bloom, N Fuel Processing Technology 2000, 63, 1-27; Wilhelm S M, Liang L, Cussen D, et al. Environmental Science & Technology, 2007, 41, 4509-4514).
Crude oil typically contains several chemical species of mercury, which differ in their chemical and physical properties. These include elemental mercury, organic mercury compounds (e.g., R2Hg and RHgX, where R═CH3, C2H5, etc., and X═Cl−, etc.) and salts of the Hg2+ ion. The latter are soluble in oil and gas condensate but preferentially partition into the water phase in primary separations. Mercuric chlorides and halides have a reasonably high solubility in organic liquids (order of magnitude more than elemental mercury). (Bloom, N. S. Fresenius' J. Anal. Chem. 2000, 366(5):438. Wilhelm, S., and N. Bloom. Fuel Proc. Technol. 2000, 63:1).